1. Field
The present disclosure relates to a cathode active material, a cathode, and a lithium battery including the same, and methods of preparing the cathode active material.
2. Description of the Related Art
Transition metal compounds, such as LiNiO2, LiCoO2, LiMn2O4, LiFePO4, LiNixCo1-xO2 (0≦x≦1), LiNi1-x-yCoxMnyO2 (0≦x≦0.5, 0≦y≦0.5), or oxides of the transition metal compounds and lithium are used as a cathode active material for a lithium battery. LiCoO2 is relatively expensive, and since a substantial electrical capacity of LiCoO2 is about 140 mAh/g, LiCoO2 has limited electrical capacity. Also, since about 50% or more of the lithium in the LiCoO2 is removed when a charge voltage is increased to about 4.2 V or more, in charged battery the LiCoO2 may be Li1-xCoO2 (x>0.5). Oxides in the form of Li1-xCoO2 (x>0.5) are structurally unstable and the electrical capacities thereof rapidly decrease as charge and discharge cycles proceed.
Cathode active materials such as LiNixCo1-xO2 (x=1, 2) or LiNi1-x-yCoxMnyO2 (0≦x≦0.5, 0≦y≦0.5), may have poor swelling suppression characteristics at a high temperature.
Li2MnO3 has a high theoretical electrical capacity of about 460 mAh/g and a high driving voltage. However, Li2MnO3 may have low ionic conductivity and electronic conductivity, and may have poor cycle characteristics and stability due to phase changes which occur during a charge and discharge process. Thus there remains a need for an improved cathode active material.